Conventionally, most loudspeaker horns have exponential curve, suspension line curve, or conical line shapes. FIG. 1 shows a conventional loudspeaker horn having an exponential curve shape. As shown in FIG. 1, such a conventional loudspeaker has a sound-generating head 1, an exponential horn 2, an exponential horn outlet section 3, and a reverser section 4. The loudspeaker horn works by utilizing a horn curve to provide certain resistance to the sound source (sound-generating head) to obtain an optimal efficiency of sound propagation. To reduce the length of horn, it is often made in three sections, in which the intermediate section is a reverser section, thus forming a folded structure, as indicated in FIG. 1, and its high-frequency response usually suffers some attenuation. Such a structure has the defect that its sound wave radiation angle at the output end is large, so the sound wave energy is not concentrated and the propagation distance is limited. For long distance and/or high-intensity broadcasting, energy must be concentrated in a small range, which can hardly be achieved using conventional loudspeakers.